Biomedical Engineering Reference
In-Depth Information
1.5 fold per year)
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will open unimagined possibilities in neuroscience research.
Neuroscientists must become aware of these exciting new techniques and use
them in interdisciplinary teams where the gaps between electronic technology
and neurology can be successfully bridged.
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4.1 Nanoparticles as Reporters of Brain Activity
A new area of advanced detection methods in neurobiology is the development
of nanoparticles. As introduced briefly in Chapter 1, nanoparticles are repre-
sented by small (5-8 nm) inorganic compounds made of semiconductor or
metallic materials with well-defined quantum states and electronic structure.
For example, they are composed of a metal core (cadmium, selenium, cadmium
telluride), a zinc sulfate shell and an outer coating functionalized using
bioactive molecules (Figure 4.1). Fluorescent quantum dots are used to
visualize molecular processes in neuron cells using fluorescent microscopy
methods. Their properties can be adjusted by changing the composition or size.
Small changes in the radius translate into distinct color changes so they can be
used to replace bulky organic fluorophores which interfere with the molecular
structure of the object of investigation. The design of these nanostructures is
based on the ability to control plasmonic behavior in metallic nanoparticles,
quantum size effects in semiconductor heterostructures with designed
asymmetries, and nanoparticles with implanted dopants possessing sharp
emission spectra. Their small sizes allow large and specific energy jumps
between the energy band gaps of excited electrons or electron-hole pairs.
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These inorganic nanoparticle optical probes can be tuned to match the
photon energy requirements of the various excitation and detection systems.
Unlike organic optical probes, they are photochemically robust during
extended interrogation. For neuroscience studies, nanoparticles are combined
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Figure 4.1
Structure of a semiconductor fluorescent quantum dot nanocrystal. The
heavy metal core is responsible for the fluorescence properties of
the quantum dot. The non-emissive shell stabilizes the core, whereas the
coating layer provides anchor sites to organic and biological ligands such
as antibodies, peptides and other organic molecules.
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(Reprinted by kind permission of the Society for Neuroscience.)
